In the manufacture of alkaline-process of making pulps, the wood is cooked with white liquor comprising NaOH, sodium carbonate, and sulfur salts of sodium such as sodium sulfate, sulfide, thiosulfide. After cooking, the liquor is evaporated, the organic materials burned and the inorganic materials are disolved to obtain the green liquor. This green liquor is generally discharged in a slaker together with lime. The lime produces calcium hydroxide which is further reacted in reactors mounted in series called causticizers, and following the causticizers, the lime mud (CaCO.sub.3) is filtered such as with rotating drums. Thus, this process generates white liquor by converting the Na.sub.2 CO.sub.3 to caustic soda (NaOH) and lime mud CaCO.sub.3, CaO+H.sub.2 O-Ca(OH).sub.2 +Na.sub.2 CO.sub.3 -2NaOH+CaCO.sub.3. The process is illustrated for instance in U.S. Pat. No. 4,536,236 dated Aug. 20, 1985 as invented by Bertelsen.